The Role of Cheater Cells in Quorum Sensing Bacterial Cultures

Cooperation is essential for the survival of microbial communities, as it enables access to resources and enhances fitness. Social cheating, where some individuals exploit the benefits of cooperation without contributing, can destabilize these communities. While traditionally seen as harmful, the frequent occurrence of cheaters in environmental bacterial populations suggests they may confer an evolutionary advantage. We investigate the role of cheater cells in bacterial populations governed by Quorum sensing (QS), which regulates the production of public goods, such as enzymes and protective biofilms, through cooperative behaviors. We model the dynamics of a bacterial population where cooperative cells can mutate into cheaters, exploiting QS-controlled public goods without incurring the associated metabolic cost. By leveraging time-scale separation and analyzing the system's equilibria, we demonstrate the existence of a stable equilibrium where both cooperative and cheater cells can coexist. We also extend our model to competing bacterial populations and show that cheaters can transiently confer a selective advantage by accelerating niche colonization. Our findings confirm that cheaters may contribute to increasing population resilience, but only if they are a limited fraction of the entire population.